Validates the body argument and any @Valid-annotated parameters of a Feign-built interface using JSR-303 / Bean Validation 2.0 (javax.validation) before the HTTP request is dispatched. Constraint violations surface as javax.validation.ConstraintViolationException.

Marked @Experimental while the underlying feign.interceptor.MethodInterceptor API stabilises.

For the Jakarta namespace, see the sibling module feign-validation-jakarta.

<dependency>
  <groupId>io.github.openfeign</groupId>
  <artifactId>feign-validation</artifactId>
  <version>${feign.version}</version>
</dependency>

Api api = Feign.builder()
    .methodInterceptor(BeanValidationMethodInterceptor.usingDefaultFactory())
    .target(Api.class, "https://example.com");

You can pass an explicit Validator and validation groups:

Validator validator = Validation.buildDefaultValidatorFactory().getValidator();
Feign.builder()
    .methodInterceptor(new BeanValidationMethodInterceptor(validator, Create.class))
    .target(Api.class, "https://example.com");

• The method's body argument (the parameter Feign treats as bodyIndex) — always.
• Any other parameter annotated with @Valid — useful for headers, query parameters carrying complex objects, etc.

Null arguments are skipped. Methods with no parameters pass through.